In relation to patients requiring mechanical ventilation for acute pulmonary failure, it is proposed: A. To use both mathematical modelling and data from patients, to refine the indices used for determining the optimum positive pressure ventilation variables, i.e., those "ventilator settings" which will result in the best pulmonary gas exchange and oxygen transport with the least lung barotrauma. B. To study right to left shunt increase during oxygen ventilation, as an index of pulmonary status, and to test the hypothesis that pulmonary vasoconstriction is an important protective mechanism against the development of increasing consolidative changes in underventilated areas. C. To determine the factors responsible for an increased cardiac index. In patients with thermal burns, it is proposed to distinguish the various categories of respiratory failure, their clinical indices and to examine various therapeutic options.